backstory - HBC user (pill.. i think a low dose, but i could be wrong), probably near perfect user (for the sake of argument, lets say typical user). Went on antibiotics (pencillan family) for 10 days for an infection. Last antibiotic pill was last thursday. Period due today (9/14). Had sex, with a condom on 9/13, and the condom broke.
I told her that even with using the antibiotics, the chance of her being pregnant were very very slim, as she was so close to her period/withdrawal bleed, and had been using her HBC as directed the entire time, never missing a pill. Of course, another friend chimed in to say how "her friend got pregnant while on HBC and antibiotics" (which doesn't ease the friend's concerns about her own issue).
She went and got plan B anyways, but VP, what do you think. Am I right in that she's got a very slim chance of becoming pregnant?